Top women's seed Victoria Azarenka of Belarus and second-seeded Maria Sharapova continued their march through the draw.

Both women, who have yet to drop a set, came through the quarterfinals unscathed, but only one played their match to conclusion.

Azarenka, the Australian Open champion, won 6-2, 6-0 over unseeded Romina Oprandi of Switzerland.

Sharapova was in charge of fifth-seeded Angelique Kerber 6-0, 3-0 when the German retired with a right foot injury.

Azarenka, the winner of four titles in seven finals this season, will meet seventh-seeded Li Na., who moved closer to becoming the first Chinese finalist when she drubbed third-seeded Agnieszka Radwanska of Poland 6-4, 6-2.

Sharapova will also seek her eighth final appearance this year — she's won three titles, including her first French Open trophy — when she plays Marion Bartoli of France. Bartoli beat Carla Suarez Navarro of Spain 6-0, 2-6, 6-4.

Azarenka dominated Oprandi, winning 60 of 87 points played, and capitalizing on all six break point opportunities.

“Sometimes it's important to stay tough and have that concentration to make sure that you can win every ball and every point,” Azarenka said.

Sharapova, the French Open champion, said she was unaware of Kerber being injured before she surrendered the match.

The Russian offered Kerber five chances to break serve, but held.

“I thought we played a high level of tennis the first set and a half, there were many games that went to deuce,” Sharapova said. “I was surprised she called the trainer and even more so when she retired quickly after that.”